The present invention relates to a turbocharger for at internal combustion engine, particularly variable speed engine.
It is preferable in turbochargers for variable speed engines to use a relatively wide compressor, since this gives maximum control. However, the thermodynamic efficiency of a turbocharger is generally compromised by increased compressor width. This is especially so when the turbine flow is controlled by a bypass or a variable geometric device. Currently the problem is addressed by cutting back the leading edge of alternate compressor blades to reduce inlet choking and thus increase the maximum flow potential. However the stability of such a turbocharger at low flow rates is poor and the overall efficiency decreased.
According to the present invention there is provided a turbocharger for an internal combustion engine, the turbocharger comprising an air intake, a compressor housing, a plurality of bypass channels formed in the compressor housing providing a short cut to air from the air intake through the housing, and means for controlling air flow through the bypass channels (1).
Preferably the means for controlling air flow through the bypass channels comprises a movable sleeve having a pattern of openings, eg. slots. The pattern of slots preferably corresponds to the pattern of channels in the housing, and the sleeve is used to selectively cover the channels fully, partially or not at all depending upon the alignment of channels and openings.
According to a one embodiment the sleeve is movable axially to control the opening of the channels.
According to a second embodiment the sleeve is slidable in a rotating motion to effect control of the air flow through the channels.
The channels may be formed in a circular pattern or an axial pattern, and the slots in the sleeve will preferably correspond.